This invention relates to combustion engines or combustors and, more particularly, to a fuel system arrangement for reducing undesirable emissions from combustion engines or combustors.
Conventional liquid-fueled combustion engines or combustors typically include a fuel system that supplies liquid fuel to a combustor. The liquid fuel reacts with oxidizer or oxidizers to produce a rapidly expanding gas that moves a piston or turbine blades, for example, to propel a vehicle or to produce heat for other applications. Disadvantageously, the combustion may result in the production of undesirable emissions, such as oxides of nitrogen (NOx), carbon monoxide (CO), uncombusted fuel (UHC), and carbonaceous soot.
Conventional combustion engines or combustors have not satisfactorily addressed the undesirable emissions. Many conventional combustion engine assemblies seek to reduce emissions by more efficiently combusting the liquid fuel in compressed air or oxidizer. This reduces only a portion of the emissions that result from incomplete combustion of the liquid fuel. The formation of some emissions, such as NOx, however, is more closely related to combustion temperature than to the efficiency of combustion. Therefore, increasing the combustion efficiency does not significantly reduce emissions of NOx.
One proposed solution for minimizing undesirable emissions includes combusting the liquid fuel in compressed air or oxidizer at a lower temperature to reduce formation of the emissions. This may reduce formation of some of the emissions, however, it increases the amount of uncombusted fuel (i.e., reduces combustion efficiency). The increase in uncombusted fuel may negate a significant portion of the benefit accrued from the reduction in the formation of the emissions.
Accordingly, there is a need for a fuel system arrangement that provides lower temperature combustion to reduce formation of emissions while maintaining combustion efficiency and combustor operability. Combustor operability relates to the maintenance of a robust; stable combustion process. Combustors with poor operability may experience “blow-out” events in which the flame is extinguished. Poor operability may also lead to large combustor pressure oscillations which can cause noise and vibration problems and decrease combustor durability. This invention addresses these needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.